An electric rotating machine is known in the art, which is used as a power source for an electric power steering device of a vehicle. In the electric rotating machine, an electric motor portion having a rotor and a stator and an electric control portion for controlling the electric motor portion are integrally formed.
Another electric rotating machine is known in the art, for example, as disclosed in Japanese Patent Publication No. 2013-153580. The electric rotating machine of this prior art has a simple structure, according to which a pair of end frames are coupled to each other by multiple through bolts and a stator is interposed between the end frames.
For example, as shown in FIG. 1 of the above prior art (JP 2013-153580) and also shown in FIG. 8 of the present application, an electric control portion is fixed to a first end frame (an upper-side end frame) of the electric rotating machine, while a second end frame (a lower-side end frame) of the electric rotating machine is fixed to an appropriate position on a side of a vehicle body.
When the electric rotating machine of this kind having the pair of end frames and the stator between the end frames is manufactured, a process for fixing the electric control portion to the first end frame and a process for inserting multiple through-bolts through the first and the second end frames are carried out on the same side of an axial end (an upper-side in the drawing) of the electric rotating machine, in view of achieving a high productivity. More exactly, the through-bolts are inserted through the first end frame at such positions, which are outside of a space for the electric control portion in a radial direction, and fastened to the second end frame.
In recent years, a diameter of the electric control portion is made to be almost equal to that of the stator of the electric motor portion. The positions for the through-bolts are restricted by the space for the electric control portion. In other words, it is difficult to locate the through-bolts at such positions closer to the stator in its radial direction. In such a structure, an axial force of the through-bolt cannot be effectively applied to the stator of the electric motor portion for firmly supporting the stator between both of the end frames.
When a function effect of the axial force of the through-bolts to the stator becomes lower, the first and the second end frames are likely to oscillate to each other. In particular, in the electric power steering device, a reaction force (a radial force) is applied to the electric rotating machine from a steering mechanism. Therefore, the first end frame, which is remote from the second end frame fixed to the vehicle body may be largely oscillated and the electric control portion fixed to the first end frame may be bent.
When the axial force of the through-bolts is made larger in order to suppress the oscillation of the end frame of the electric rotating machine, the first and/or the second end frames maybe bent in the axial direction, that is, in a direction closer to each other unless the axial force is properly applied to the stator provided between the first and the second end frames. As a result, the electric control portion may be bent.
As above, it is a problem in the electric rotating machine in the prior art that a mechanical stress may be applied to the electric control portion, which is mounted to the first end frame.